DHA Pharmacist Pharmaceutical Sciences 2 — Questions and Answers
Question 1: What is the purpose of a preservative in a multi-dose ophthalmic solution?
- To prevent microbial contamination between uses (Correct answer)
- To increase drug potency
- To enhance colour for patient identification
- To extend drug shelf life at high temperatures
Correct answer: To prevent microbial contamination between uses
Preservatives such as benzalkonium chloride in multi-dose eye drops prevent bacterial and fungal contamination after the container is opened and used repeatedly.
Question 2: Which dosage form provides the most rapid onset of systemic drug action after oral administration?
- Oral solution
- Enteric-coated tablet
- Extended-release capsule
- Sublingual tablet (Correct answer)
Correct answer: Sublingual tablet
Sublingual tablets dissolve under the tongue, where drugs are rapidly absorbed directly into systemic circulation through the oral mucosa, bypassing hepatic first-pass metabolism.
Question 3: What does 'hygroscopic' mean in pharmaceutical storage?
- The substance readily absorbs moisture from the surrounding air (Correct answer)
- The substance is sensitive to light
- The substance is volatile at room temperature
- The substance degrades at low temperatures
Correct answer: The substance readily absorbs moisture from the surrounding air
Hygroscopic substances absorb water vapour from the environment, which can alter drug stability, potency, and physical form, requiring storage in airtight containers.
Question 4: What is the significance of a drug's pKa value in pharmacokinetics?
- It determines the pH at which the drug is 50% ionised and 50% un-ionised, affecting membrane permeability (Correct answer)
- It indicates the drug's melting point
- It measures solubility in water
- It defines the drug's molecular weight
Correct answer: It determines the pH at which the drug is 50% ionised and 50% un-ionised, affecting membrane permeability
At a pH equal to the pKa, a drug exists in equal proportions of ionised and un-ionised forms; this ratio governs how easily the drug crosses lipid membranes for absorption and distribution.
Question 5: Which excipient category is used to increase tablet hardness and provide bulk in solid dosage forms?
- Diluents/fillers (e.g., lactose, microcrystalline cellulose) (Correct answer)
- Lubricants (e.g., magnesium stearate)
- Disintegrants (e.g., croscarmellose sodium)
- Binders (e.g., polyvinylpyrrolidone)
Correct answer: Diluents/fillers (e.g., lactose, microcrystalline cellulose)
Diluents or fillers like lactose and microcrystalline cellulose add bulk and improve compressibility to achieve the required tablet weight and hardness.
Question 6: What is meant by the term 'therapeutic equivalence' between two drug products?
- Both products are pharmaceutically equivalent and produce the same clinical effect when administered to patients under specified conditions (Correct answer)
- They have the same name but different manufacturers
- They have the same active ingredient but different strengths
- They are produced in the same country
Correct answer: Both products are pharmaceutically equivalent and produce the same clinical effect when administered to patients under specified conditions
Therapeutic equivalents are pharmaceutically equivalent products demonstrated to produce the same clinical outcomes, meaning they can be substituted for each other safely in clinical practice.
DHA Pharmacist Pharmaceutical Sciences 2
What is the purpose of a preservative in a multi-dose ophthalmic solution?